Method for recognising a change in lane of a vehicle

ABSTRACT

A method of detecting a lane change of a subject vehicle ( 20 ), having a locating device ( 10 ) which uses angular resolution for locating vehicles (VEH 1 , VEH 2 , VEH 3 ) traveling in front, and a device ( 44 ) for determining the yaw rate (ω 0 ) of the subject vehicle. The angular velocity (ω i ) of at least one vehicle traveling in front relative to the subject vehicle ( 20 ) is measured using the locating device ( 10 ), and a lane change signal (LC) indicating the lane change is formed by comparing the measured angular velocity (ω i ) to the yaw rate (ω 0 ) of the subject vehicle.

BACKGROUND INFORMATION

[0001] The present invention relates to a method of detecting a lanechange of a vehicle having a locating device which uses angularresolution for locating vehicles traveling in front, and a device fordetermining the yaw rate of the subject vehicle.

[0002] Distance- and speed-regulating devices for motor vehicles, alsoreferred to as ACC (adaptive cruise control) systems, are known. Inthese systems, objects, for example vehicles traveling in front in thesame lane as the subject vehicle, are detected using a locating device,for example a radar system which provides angular resolution, whichenables the distance and relative speed of the vehicle traveling infront to be measured. The capability for angular resolution in such aradar system has been used in the past to check the detected objects forplausibility, so that, for example, vehicles in the same lane as thesubject vehicle may be distinguished from road signs or markings on theedge of the roadway, or from vehicles in other lanes.

[0003] When a vehicle traveling in front in the same lane as the subjectvehicle is within the locating range of the radar, the traveling speedis regulated by intervention in the drive or braking system of thevehicle in such a way that a speed-dependent distance from the vehicletraveling in front is maintained. On the other hand, if there is novehicle within locating range in the same lane as the subject vehicle,the device regulates the speed at an intended speed selected by thedriver.

[0004] German Patent Application 196 37 245 A1 describes an ACC systemin which the evaluation of the radar signal for plausibility is modifiedwhen the driver indicates his/her intention to change lanes by actuatingthe left or right turn indicator. In this situation, the travel corridortaken into account in regulating the distance is temporarily extended tothe future new lane, and the vehicles in the former lane as well as thevehicles in the future lane are taken into account in regulating thedistance. The travel corridor is defined as a strip of fixed, oroptionally variable, width on both sides of the prospective travel pathof the subject vehicle. For a straight roadway course, the travel pathof the subject vehicle is indicated by a straight line running in thedirection of travel through the center of the vehicle. For a curvedroadway course, it may be assumed as an approximation that theprospective travel path is a curve of constant curvature. Assuming asteady-state curve situation, the particular curvature may be calculatedby defining the yaw rate of the subject vehicle via the traveling speed.In principle, the yaw rate may be determined from the steering angle andthe traveling speed, but preferably is directly measured using a yawrate sensor, in particular since such a yaw rate sensor is alreadypresent in vehicles having an electronic stability program (ESP).

[0005] In non-steady state situations, however, in particular during alane change, an accurate determination of the travel corridor has provento be difficult. Merely evaluating the signal from the turn indicator isof no further use here, since actuation of the turn indicator onlyindicates the intention to change lanes but does not allow the detectionof exactly when the lane change starts and ends. Even making additionalallowance for the steering commands of the driver does not enable thelane change to be unambiguously detected, since a curved roadway coursemay also give rise to the steering commands. In the past, theseuncertainties in the detection of a lane change have often causedmalfunctions in the regulating system due to the fact that during thelane change the radar beam temporarily sweeps over the edge of theroadway and identifies stationary targets such as road signs or the likeas presumably relevant objects, or that for roadways having three ormore lanes, vehicles in the next-to-adjacent lane are erroneouslyassociated with the travel corridor of the subject vehicle. Toaccurately associate objects detected using the locating device with therelevant travel corridor of the vehicle, it would therefore be desirableif a lane change could be reliably identified.

OBJECT, ACHIEVEMENT, AND ADVANTAGES OF THE INVENTION

[0006] The object of the present invention is to provide a method whichallows a lane change to be more accurately detected.

[0007] This object is achieved according to the present invention by thefact that the angular velocity of at least one vehicle traveling infront relative to the subject vehicle is measured using the locatingdevice, and a lane change signal indicating the lane change is producedby comparing the measured angular velocity to the yaw rate of thesubject vehicle.

[0008] The present invention is based on the concept that, during a lanechange, in contrast to traveling along a curve, there is a distinctnegative correlation between the relative angular velocity of vehiclestraveling in front and the yaw rate of the subject vehicle. This is dueto the fact that at the start of a lane change the subject vehicleundergoes a yawing motion, and thus a rotation about the vertical axis,with a relatively high yaw rate, i.e., a relatively high angularvelocity, whereas the objects detected by the locating device do nottake part in this rotation and therefore have an angular velocityrelative to the subject vehicle which is equal in terms of actual amountbut opposite in direction. When traveling through a curve of constantcurvature, however, the subject vehicle and the vehicles traveling infront—at the same traveling speed—undergo the same rotation, so that therelative angular velocity of the vehicles traveling in front remainsapproximately zero. Only during travel into or out of a curve is itpossible for a definite difference between the relative angular velocityof the vehicle traveling in front and the yaw rate of the subjectvehicle to appear, although these differences generally are considerablysmaller than those during a lane change. Comparing the relative angularvelocities to the yaw rate of the subject vehicle thus provides a veryreliable criterion for detecting a lane change.

[0009] Advantageous embodiments of the present invention result from thesubclaims.

[0010] Since at higher traffic densities multiple vehicles traveling infront are generally simultaneously detected by the locating device, itis preferable to form a composite angular velocity from the measuredrelative angular velocities of several or all of the detected vehicles,for example by forming an average, or a weighted average based on thedistance or angle. By assigning greater weight to vehicles which haveonly a slight angular deviation from the path of the subject vehicle, itis possible to reduce interference effects caused by the relative speedsof the vehicles traveling in front. Similarly, by assigning greaterweight to vehicles only a small distance from the subject vehicle,interference effects which appear when entering into a curve arereduced. However, the noise from the angular signal of vehicles in closeproximity is generally increased because of the motion of these samevehicles. To suppress such noise, in addition to information on thevehicles it is usually possible to also collect time-specificinformation. Since the radar measurements are typically repeatedperiodically in a fixed regulating cycle, information is provided overmultiple regulating cycles, so that here as well, a lower weight may beassigned to the older cycles.

[0011] In addition, a plausibility effect may occur during thedetermination of the composite angular velocity. For example, for threeor more vehicles which are being localized it may be practical toeliminate outliers whose angular velocity clearly deviates from theother vehicles. Thus, it is possible in particular to reduceinterference effects caused by a lane change of one of the vehiclestraveling in front. If only two vehicles traveling in front are withinthe locating range, generally a lane change by one of the vehiclestraveling in front is assumed only if one of these vehicles starts topass or completes the passing maneuver. These situations may beidentified using data on the measured distance and relative angularvelocity.

[0012] Based on similar considerations, it may be advantageous forvehicles which have just appeared in the locating range because theyhave passed the subject vehicle not to be included in the calculation ofthe composite angular velocity unless a certain time delay has occurred.

[0013] In the determination of the relative angular velocities of theindividual vehicles, it may be useful to apply a correction due to therelative speeds of these vehicles. For example, a vehicle which has justbeen passed by the subject vehicle has a relative angular velocity thatis different from zero, without this indicating that the subject vehiclehas changed lanes. This relative angular velocity is proportional to theproduct of the relative speed and the angle at which the vehicle islocalized, divided by the distance of this vehicle, and may beeliminated by subtracting an appropriate correction factor.

[0014] If the composite angular velocity ω_(e) of the vehicle travelingin front and the yaw rate ω₀ of the subject vehicle were determined, asignal LC is obtained which indicates with high reliability a lanechange of the subject vehicle by forming the negative of thecross-correlation value of these variables: LC=−ω₀*ω_(e)/(ω_(e)+ω₀). Assoon as this signal exceeds a specified threshold value, it can beassumed that a lane change of the subject vehicle is occurring.

[0015] Optionally, the signal from the turn indicator may also be takeninto account in such a way that when the turn signal is actuated, thethreshold value to which signal LC is compared is decreased. It is alsopossible to distinguish whether the left or the right turn indicator wasactuated, so that the threshold value is decreased only when the lanechange occurs in the correct direction. The direction of the lane changeis specified by the algebraic sign of ω₀.

[0016] Yaw rate signal ω₀ may also be checked for a pattern which istypical of a lane change in order to increase the reliability of theinformation. During a lane change this: signal exhibits a characteristicS-shaped curve. According to a further embodiment of the presentinvention, the expected completion of the lane change as well may bepredicted from this pattern. Alternatively, it may be assumed that thelane change is completed when a certain time period, which optionally isspeed-related, has elapsed after the lane change is detected.

[0017] The lane change signal thus obtained may be used within the scopeof an ACC system and in many other ways as well. In particular, thetravel corridor of the subject vehicle may be appropriately adjustedduring detection of the start of a lane change. It is also possible totake into account that at the midpoint of the lane change the directionof travel of the subject vehicle deviates from the direction of theroadway. The value of this angular deviation may be quantitativelydetermined by integrating the yaw rate signal, the composite angularvelocity signal, or a combination of both over time, and may then beused to correct the predicted travel path and thus the travel corridor.In this manner it is possible to prevent the erroneous evaluation ofstationary targets during the lane change. In one even simplerembodiment, this effect may also be achieved by reducing the penetrationdepth of the locating device so that objects farther away continue to bedisregarded in the distance regulation.

[0018] In addition, the lane change signal may be used to temporarilyextend the travel corridor to the adjoining lane which forms the futurelane, and to narrow the travel corridor back to the new lane after thelane change is completed. Likewise, it is possible to use the lanechange signal to trigger certain additional functions which areimplemented in the ACC system, for example a passing aid which assistsin merging into the flow of traffic in the future lane by automaticallyaccelerating or decelerating the vehicle. The lane change signal mayalso be evaluated for special functions besides the actual ACCregulation, for example for lighting control which automatically adjuststhe beam direction from the headlights of the vehicle.

[0019] Regulating systems are also known which detect the course of theroadway by evaluating a camera image or by using other sensors, andwhich assist the vehicle in staying within the lane (lane keepingsupport) by intervening in the steering of the vehicle. When the vehicleis equipped with such a system, it is possible not only to detect thelane change directly by evaluation of the sensor signals which sense theedge of the roadway, but in this case also to use the method accordingto the present invention for plausibility testing.

BRIEF DESCRIPTION OF THE DRAWING

[0020] An exemplary embodiment of the present invention is described inmore detail below with reference to the drawing.

[0021]FIG. 1 shows a block diagram of a distance- and speed-regulatingsystem for motor vehicles which is designed to carry out the methodaccording to the present invention;

[0022]FIG. 2 shows a diagram of a three-lane roadway having travelcorridors in which vehicles traveling in front which are relevant to thedistance regulation are situated;

[0023]FIG. 3 shows a diagram corresponding to FIG. 2 which illustrates alane change of the subject vehicle;

[0024]FIG. 4 shows the time curve of various variables whichcharacterize the lane change illustrated in FIG. 3;

[0025]FIG. 5 shows a diagram of a driving situation in which theregulated vehicle and a vehicle traveling in front are driving out of acurve; and

[0026]FIG. 6 shows the time curve of the same variables as shown in FIG.4 for the driving situation illustrated in FIG. 5.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0027] Because the design and operating principle of a distance- andspeed-regulating system, referred to below as an ACC system, are knownas such, FIG. 1 shows only those components of such a system that areimportant for understanding the present invention.

[0028] A radar sensor 10 is provided as a locating device for vehiclestraveling in front, and is mounted on the front of the regulated vehicleand periodically locates target objects situated in front of thevehicle, for example vehicles traveling in front, and stationary targetson the edge of the roadway. By evaluating the radar echo, signals areproduced, either in the radar sensor itself or in a processing unitconnected downstream, which indicate the distance d_(i), the relativespeeds v_(i) (in the radial direction), and the azimuth angles ψ_(i) ofthe located objects. The azimuth angles here are defined with respect tothe instantaneous straight-ahead direction of the vehicle. Positiveazimuth angles correspond to an angular deviation in the mathematicallypositive sense, and thus to the left.

[0029] An electronic regulating device 12 evaluates the data sent byradar sensor 10 and intervenes in the drive system and, if appropriate,also in the braking system of the vehicle in order to regulate the speedof the vehicle to maintain a suitable, speed-dependent distance from thevehicle traveling immediately in front in the same lane as the subjectvehicle. If no vehicle traveling in front is localized, the deviceregulates the speed at an intended speed selected by the driver.Stationary targets on the edge of the roadway are differentiated fromvehicles traveling in front based on the angular signals and therelative speed. Since the ACC system is provided primarily for use onmultilane freeways and highways, the lane in which the vehicles aresituated must also be distinguished for vehicles traveling in front.Normally, only the vehicles in the same lane as the subject vehicle aretaken into account for the distance regulation.

[0030]FIG. 2 shows as an example a one-directional roadway having threelanes 14, 16, and 18. A vehicle 20 equipped with the ACC systemaccording to FIG. 1, referred to below as the “subject vehicle,” travelsin right lane 14, and vehicles 22, 24, 26, and 28 traveling in front aresituated in lanes 14 and 16. For the distance regulation, only the datafrom vehicles 22 and 24 situated within a limited distance range in atravel corridor 30, which ideally coincides with lane 14, are taken intoaccount. Travel corridor 30 is defined as a strip of predetermined widthon both sides of path 32 which is expected to be followed by subjectvehicle 20, and is indicated by a dotted-dashed straight line in FIG. 2.In the example shown, a straight roadway course and a correspondingstraight-line path 32 are present. Methods for predicting the travelpath on a curved roadway are known as such, and will not be describedhere in further detail. To decide whether a vehicle is situated withintravel corridor 30, a path offset y is determined for each localizedobject, and a check is performed as to whether, in terms of actualamount, this path offset is less than a threshold value corresponding toone-half of the typical width of a lane. Path offset y, which in FIG. 2is shown for vehicle 26, may be calculated from measured distance d andazimuth angle ω of the affected vehicle, and corresponds approximatelyto the product d*_(ψ).

[0031] If the driver of subject vehicle 20 decides to change to middlelane 16, vehicles 26 and 28 situated in travel corridor 34 correspondingto the adjoining lane are also to be taken into account for the distanceregulation. After the lane change is completed, if subject vehicle 20 istraveling approximately in the middle of lane 16, only travel corridor34 is of significance, which however is then defined by the same pathoffset y as was travel corridor 30 originally. During the lane change,subject vehicle 20 temporarily changes its direction relative to lanes14, 16, so that prospective path 32 which is defined by thestraight-ahead direction of the vehicle no longer corresponds to theactual course of the roadway.

[0032] To enable a consistent distance regulation, even during a lanechange, and to avoid malfunctions that may irritate the driver or causediscomfort, a method is described here which allows the beginning andalso the completion of a lane change to be automatically detected.

[0033] As shown in FIG. 1, signals ψ_(i) sent by distance sensor 10which indicate the azimuth angle of the localized objects are led to adifferentiation element 36 which calculates the associated relativeangular velocities ω_(i). In practice, this may be carried out so thatthe azimuth angles measured in successive regulating cycles aresubtracted from one another, and the difference is divided by theduration of the regulating cycle (in the range of 1 ms). To suppressnoise effects, the raw data thus obtained may subsequently undergolow-pass filtering using a suitable time constant of 0.5 s, for example.

[0034] Filtered relative angular velocities ω_(i) are then corrected forrelative speed-dependent effects in a correction module 38. The natureand purpose of this correction are explained below.

[0035] Corrected relative angular velocities ω′_(i) are linked in alogic circuit 40 to form a composite angular velocity ω_(e) whichrepresents a measure of the change in the angle of the overall compositeof all vehicles 22, 24, 26, and 28 traveling in front, relative tosubject vehicle 20. Only vehicles traveling in front are taken intoaccount in the calculation of composite angular velocity ω_(e), whereasthe signals from stationary targets remain disregarded. In the simplestcase, the logic operation results in the formation of an average of allvehicles traveling in front; i.e., the sum of relative angularvelocities ω′_(i) of all vehicles traveling in front is divided by thenumber of vehicles taken into account. Composite angular velocity ω_(e)is then compared to yaw rate 107 ₀ of subject vehicle 20 in a comparatorcircuit 42. To determine yaw rate ω₀, in the example shown a generallyknown yaw rate sensor 44 is used which measures the Coriolis force whichappears during a yaw motion of the vehicle, it being possible to alsoevaluate the signals from the yaw rate sensor within the scope of astability regulation for subject vehicle 20. Any systematic error(offset) of yaw rate sensor 44 may be eliminated, if needed, by takinginto account the signals from a steering wheel angle sensor, atransverse acceleration sensor, a wheel speed sensor, and the like. Theindividual signals are also checked for plausibility, and innon-plausible situations a conclusion is made as to the failure of thesensor. The signal from yaw rate sensor 44 may also undergo low-passfiltering, preferably using the same time constants as for the relativeangular velocity signals.

[0036] In comparator circuit 42 a lane change signal LC is formed fromcomposite angular velocity ω_(e) and yaw rate ω₀ according to thefollowing formula:

LC=−ω _(e)*ω₀/(ω_(e)+ω₀)  (1)

[0037] Lane change signal LC is sent to regulating device 12 which, bycomparing this signal to a suitable threshold value (symbolized by athreshold value switch 46 in FIG. 1), detects that a lane change bysubject vehicle 20 is occurring and then makes the appropriateadjustments in the distance regulation, in particular in thedetermination of the travel corridor.

[0038]FIG. 3 shows the course over time of a lane change of subjectvehicle 20, in this case from middle lane 16 to left lane 18. FIG. 4shows the corresponding time curve for yaw rate ω₀, composite angularvelocity ω_(e), and lane change signal LC.

[0039] At time t₀ the lane change has not yet begun, and the pathdirection of subject vehicle 20 remains parallel to the lane. Yaw rateω₀ is consequently zero. Relative angular velocity ω₁ of vehicle VEH1traveling directly in front in lane 16 is also zero. For vehicles VEH2and VEH3 in the adjoining lanes, however, this is true only if theirrelative speed is zero, i.e., if their respective distances to subjectvehicle 20 remain unchanged. On the other hand, if subject motor vehicle20 has a higher speed than vehicle VEH2 in lane 14, the (negative)azimuth angle ψ₂ for the latter vehicle increases in terms of actualamount, resulting in a negative relative angular velocity ω₂ Similarly,a negative relative angular velocity ω₃ likewise results for vehicleVEH3 in the adjoining left lane if this vehicle is faster than thesubject vehicle. Thus, without additional corrections a negativecomposite angular velocity would result during the formation of anaverage. To compensate for this effect, correction element 38 makes thefollowing correction:

ω′_(i)=ω_(i) −V _(i)*ω₀ /d _(i)   (2)

[0040] As a result of this correction, at time to composite angularvelocity ω_(e) obtained from the formation of the average is also zero.Lane change signal LC produced according to equation (1) also has avalue of zero.

[0041] Between times t₀ and t₂, subject vehicle 20 veers left to theadjoining lane, and during this phase has a positive yaw rate which attime t₁ is at a maximum. The path direction of subject vehicle 20 alsochanges, corresponding to the yaw motion. Because the azimuth anglemeasured by location sensor 10 is based on this changed path direction,composite angular velocity ω_(e) assumes a value equal to the yaw ratecoo in terms of actual value, but with an opposite sign. The product ofthe yaw rate and the composite angular velocity is therefore negative,and LC accordingly assumes a relatively high positive value. At time t₂the yaw rate of subject vehicle 20 has again decreased to zero, and acountermotion is initiated for veering into the new lane. At this momentLC again returns to zero. In contrast, composite angular velocity ω_(e)still has a small negative value. This is due to the fact that the pathdirection of subject vehicle 20 at time t₂ is not parallel to the pathdirection of the vehicles traveling in front. For vehicles VEH 1 andVEH2 in particular, this results in a negative relative angular velocityeven when the relative speed has not become zero. Consequently, the zerocrossing of curve ω_(e) does not occur until a later time, so that LCtemporarily assumes negative values.

[0042] At time t₃, yaw rate ω₀ reaches a minimum and composite angularvelocity ω_(e) is at a maximum, and LC also increases again to amaximum. All signals then decrease again to zero until the lane changeis completed at time t₄.

[0043]FIG. 4 shows that the lane change is marked by a characteristicS-shaped curve for yaw rate ω₀ and by a characteristic “camel hump” forlane change signal LC. Threshold value sensor 46 detects the start of alane change by the fact that lane change signal LC exceeds a specifiedthreshold value TH (at time t_(s) in FIG. 4). A short-term drop belowthis threshold value at approximately time t₂ indicates the midpoint ofthe lane change process, whereas another drop below threshold value THat time t_(e) indicates the end of the lane change.

[0044] For purposes of comparison, FIGS. 5 and 6 illustrate a drivingsituation in which no lane change takes place, but instead subjectvehicle 20 and a vehicle VEH1 traveling in front travel out of a curve.The positions of both vehicles at time t₁ are marked by bold lines inFIG. 5, while the positions at time t₂ are marked by thinner lines, andat time t₃ by dashed lines.

[0045] At time t₁ both vehicles are still in the curve. Subject vehicle20 has a positive yaw rate ω₀. However, for vehicle speeds which areapproximately the same, the positions of subject vehicle 20 and vehicleVEH1 relative to one another remain unchanged, so that composite angularvelocity ω₀ (which in this case only is indicated by ω′₁) has a value ofzero. Consequently, LC is also zero. This means that traveling through acurve is not erroneously interpreted by the system as a lane change.

[0046] Vehicle VEH1 traveling in front begins to travel out of the curvebetween points t₁ and t₂. Its relative angular velocity thereforedecreases, while yaw rate ω₀ of the subject vehicle remains constant.Lane change signal LC is therefore positive and assumes a flat maximumat t₂. However, since multilane freeways generally have very large radiiof curvature, the yaw rates and relative angular velocities which appearhere are very low, so that lane change signal LC remains below thresholdvalue TH.

[0047] As a variant of the described method, for signal ω₀ which is usedto calculate lane change signal LC it is not the actual measured yawrate that is used, but instead the instantaneously measured yaw rateminus a moving average from the previously measured yaw rates. Whentraveling through a curve at a constant actual yaw rate, the movingaverage would then gradually approach the instantaneous yaw rate, sothat signal ω₀ would decrease essentially to zero. Consequently, lanechange signal LC between times t₁ and t₂ in FIG. 6 would remain smaller.After time t₂ the instantaneous yaw rate would decrease below the movingaverage, with the result that signal ω₀ would be negative. Signal LCwould thus also be negative between times t₂ and t₃. Thus, in thisvariant, threshold value TH could be reduced to increase the sensitivityof the lane change detection.

[0048] Regulating device 12 may react in different ways to the detectionof a lane change, at time t_(s) in FIG. 4, depending on the embodiment.For example, the ranging depth of the radar sensor may be reduced sothat regulating device 12 then responds to vehicles traveling in frontonly when they are a very small distance in front of subject vehicle 20and there is a danger of imminent collision. Thus, if the path directionof subject vehicle 20 runs at an angle to the roadway, at time t₂ inFIG. 3, irrelevant objects situated outside the lanes of interest areprevented from being evaluated.

[0049] In another embodiment, the original travel corridor is “frozen”when a lane change is detected. This may be achieved by integratingmeasured yaw rate ω₀ from time t_(s) forward. The integral then providesapproximately the angle of the instantaneous path direction of thevehicle relative to the direction of the roadway. If this angle issubtracted from measured azimuth angle ψ_(i), the result corresponds tothe subject vehicle for remaining in the original travel corridor.

[0050] Alternatively, the evaluation of the location signals at timet_(s) may be limited to those vehicles that were present in theinstantaneous travel corridor prior to that time. This is possiblebecause location data d_(i), v_(i), and ψ_(i) measured from oneregulating cycle to another for the same vehicle respectively differonly very slightly from one another, so that the individual vehicles maybe identified and their motions tracked. Additionally, a collisionavoidance strategy may be pursued in which the system responds tovehicles, not previously taken into account, when these vehicles are avery small distance in front of subject vehicle 20.

[0051] The signal of the turn indicator may also be included in theevaluation. In the situation shown in FIG. 2, when the driver's intentto make a lane change by actuation of the turn indicator is detectable,the travel corridor may be extended to a combination of both travelcorridors 30 and 34. At the same time, threshold value TH may be reducedso that the actual start of the lane change is detected earlier. At thedetected start of the lane change, the extended travel corridor is thenfrozen, and finally, when the end of the lane change is detected att_(e), the travel corridor is narrowed to new travel corridor 34.

What is claimed is:
 1. A method of detecting a lane change of a subjectvehicle (20) having a locating device (10) which uses angular resolutionfor locating vehicles (VEH1, VEH2, VEH3) traveling in front, and adevice (44) for determining the yaw rate (ω₀) of the subject vehicle,wherein the angular velocity (ω_(i)) of at least one vehicle travelingin front relative to the subject vehicle (20) is measured using thelocating device (10), and a lane change signal (LC) indicating the lanechange is formed by comparing the measured angular velocity (ω_(i)) tothe yaw rate (ω₀) of the subject vehicle.
 2. The method as recited inclaim 1, wherein, before a comparison to the yaw rate (ω₀) of thesubject vehicle is made, the measured relative angular velocity (ω_(i))of the vehicle traveling in front is corrected, resulting in a relativeangular velocity (ω′_(i)) which is independent of the relative speed(v_(i)) of the vehicle traveling in front.
 3. The method as recited inclaim 1 or 2, wherein from the corrected or uncorrected relative angularvelocities (ω_(i), ω′_(i)) of multiple vehicles (VEH1, VEH2, VEH3)traveling in front a composite angular velocity (ω_(e)) is formed whichrepresents a relative change in the angle of the combination of vehiclestraveling in front, and the yaw rate (ω₀) of the subject vehicle iscompared to this composite angular velocity (ω_(e)).
 4. The method asrecited in claim 3, wherein the composite angular velocity (ω_(e)) is aweighted or unweighted average of the corrected or uncorrected relativeangular velocities (ω_(i), ω′_(i)) of the vehicles traveling in front.5. The method as recited in one of the preceding claims, wherein thesignal from a yaw rate sensor (44) is evaluated as the yaw rate (ω₀) ofthe subject vehicle (20).
 6. The method as recited in one of thepreceding claims, wherein the lane change signal (LC) is calculatedaccording to a formula which gives a high positive value when the yawrate (ω₀) of the subject vehicle and the relative or composite angularvelocity (ω_(i), ω_(e)) are different from zero in terms of actualamount and have opposite algebraic signs.
 7. The method as recited inclaim 6, wherein to calculate the lane change signal (LC) thecross-correlation of the yaw rate (ω₀) of the subject vehicle iscalculated using the relative or composite angular velocity (ω_(i),ω_(e)).
 8. The method as recited in one of the preceding claims, whereinthe beginning of a lane change is detected by the fact that the lanechange signal (LC) exceeds a specified threshold value (TH).
 9. Themethod as recited in claim 8, wherein the threshold value (TH) isreduced when a turn indicator of the subject vehicle (20) is actuated.10. The method as recited in claim 8 or 9, wherein the completion of thelane change is detected when the lane change signal (LC) falls below thethreshold value (TH) for the second time after the beginning of the lanechange is detected.